The electrical potentials generated by neurons, primary afferent fibers and glia cells, will be studied during seizure activity caused by toxic dose of penicillin and other epileptogenic procedures in spinal cord and cerebral cortex. The electrical properties of cells, extra-cellular potassium concentration, and the metabolic activity (oxidation of NADH) will be measured in situ. The following specific questions are asked: (1) Does K ion discharged from active neurons play a part either in the initiation of seizures, or in their maintenance and spread, once they begin? (2) Are clonic cell discharges synchronized by the action of extra-cellular current? (3) What protects a spinal gray matter from the occurence of spreading depression? (4) Does penicillin have a direct toxic effect on cell membranes? (5) Are partially denervated mammalian central neurons spontaneously active? And are they supersensitive to the excitatory transmitter of which they were deprived by the denervation? (6) What is the relationship between cerebral and spinal seizure patterns? BIBLIOGRAPHIC REFERENCES: E.W. Lothman and G.G. Somjen. Motor and electrical signs of epileptiform activity induced by penicillin in the spinal cord of decapitate cats. Electroenceph. Clin. Neurophysiol. (In press, 1976). E.W. Lothman and G.G. Somjen. Functions of primary afferents, and responses of extracellular K ion during spinal epileptiform seizures. Electroenceph. Clin. Neurophysiol. (In press, 1976).